Ambulatory paraffin scraper



Jan. 24, 1961 AMBULATORY PARAFFIN SCRAPER Filed July 16, 1957 I I E I! INVENTOR J'A I IES C. TRIPPLEHORN ATTORNEY AMBULATORY PARAFFIN SCRAPER James C. Tripplehorn, 1013 Mary Ellen St., Pampa, Tex. Filed July 16, 1957, Ser. No. 672,266

2 Claims. (Cl. 166-176) This invention relates to parafiin scrapers of the type intended to surround a sucker rod while the latter. is being reciprocated within a tubing string during pumping of an oil well, and more particularly the invention relates to ambulatory paraffin scrapers which are free to move up and down with respect not only to the tubing but also with respect to a length of the sucker rod which the scraper surrounds, the scraper also serving as a rod guide to center the rod in the tubing.

It is a principal object of this invention to provide a paraffin scraper which is free to move axially on the sucker rod which it surrounds so as to prevent the building up of parafiin deposits on the sucker rod itself, the travel of the scraper being confined to the particular sucker rod, or being confined to a certain portion of the length of one rod by abutments which may comprise fixed types of rod guides or scrapers which are not free to move axially of the rod.

It is another primary object of this invention to provide an ambulatory paraffin scraper which may be installed on a standard rod having standard tool joints without the necessity of severing the rod or otherwise altering it.

It is another major object of this invention to provide a paraflin scraper which is in the form of an open helix having a central bore therethrough adapted to receive and freely pass the sucker rod, the inside diameter of the helix being larger than the sucker rod and the outside diameter of the helix being smaller than that of the pump tubing in which the sucker rod and scraper are intended to operate. The open helix form provides a minimum restriction of the oil passage space between the sucker rod and the well tubing-while the abrupt meetings of the-inner and outer helix surfaces with its side surfaces provide scraping edges which are satisfactory for scraping both the sucker rod which passes through the center of the helix and also for scraping the inner surface ofthe tubing. The present paraflin scraper takes the form of a plurality of spaced convolutions which maybe cut off at any desired point to'secure a scraper of whatever length is required to give satisfactory scraping performance in a particular well. The only restriction on the length of the helix is that it should be suificiently long that it cannot turn crosswise in the tubing and become wedged therein. Probably 1 /2 to 2 convolutions would suffice to hold the axis of the helix in alignment with the axis of the sucker rod in a satisfactory manner.

It is a further very important object of the present invention to provide a parafiin scraper which is made of a plastic which can be shaped and then hardened to retain its shape, and in addition which plastic, at the temperatures encountered in oil wells, is dimensionally stable and resistant to attack by oil and acids. The electrical insulating properties of the plastic are also important since they prevent the attack on other adjacent metal parts in the well by electrolysis. A range of suitable plastics includes the following:

Vinylidene chlorideRigid compound.

Patented Jan. 24, 1961 ice ' Polytetra-Fluoro ethylene. Polycloro-Tri fiuoro ethylene.

sion process or by some other plastic handling process'in -Polymethyl alpha cloroAcrylate. Polyester diallyl phthalate.

Poly acetal resin.

1 The use of plastic in connection with such a helix is important for several reasons. In the first place, manufacturing of such a product can be conveniently and economically carried out either by molding or by an extruorder to produce the desired form. In addition to the 'multiple advantages which the plastic has over metals,

plastics found in the above range also exhibit springlike qualities generally thought of in connection with v metals, which spring-like qualities permit the scraper to flex without damage or breakage. Another advantage'in the use of the above plastics results from the fact that the very substance to be scraped by the scraper, namely "the paraffin, has very little tendency to stick to the plastic scraper since paraflin does not tend to adhere to the smooth non-porous surface. Therefore, the build-up which occurs on metal paraffin scrapers is substantially i that of the well liquids will migrate through consider- 1 able distances during reciprocation of the sucker rod within the well tubing. For example, in'the case where "the stroke of the sucker rod in the tubing is 3 feet, a relatively short scraper,-perhaps only a foot or so long, will clean a 10 or 15 foot vertical length of sucker rod -and tubing despite -the relatively short stroke of' the pump. Because of the fact thatthe specific gravity of the-helix is nearly'the same as that ofthewell'liquids,

the helix will workits way along the tubing from one abutment tothe next adjacent abutment even though this stroke-and many times the length of the scraper.

distance may be many times the length of the pump The 1 scraper, ofcourse, does not pass over such a length of -sucker rod-in one or two strokes, but may require a considerable time to cover the greater length. Tests have shown, however, that it does periodically cover such a length and that such coverage tends to be repeated at regular' enough intervals that the ambulatoryscraper -will satisfactorily preventlthe building up: ofuparaffin deposits on both the rod and the tubing. It is well known that the well fluids are not homogeneous but contain oil and water, more or less solid objects, lumps of paraflin, and gas pockets. This non-homogeneous character of the fluid which is being pumped upwardly perhaps accounts for the fact that the scraper is caused to reciprocate over a greater length of rod and tubing than the length of the stroke.

A further object of the invention is to provide a paraflin scraper which as it is reciprocated performs rotational motion which tends to reverse in direction as the direction of reciprocation of the rod in the tubing is reversed. This rotational-reciprocating action exhibits excellent scraping characteristics.

It is another object of the present invention to provide a flattened surface at each end of the helical scraper,

which surface lies in a plane disposed normal to the axis of the helix, and serves as a land" for contacting the abutments which confine the ambulatory scraper to a certain portion of the sucker rod.

It is still another object of the invention to provide a helical scraper capable of economical manufacture in one of a number of different cross-sectional forms, each one of which will give satisfactory scraping performance. Other objects and advantages of the present invention will become apparent in the following discussion of i the drawing wherein:

Figure 1 is an elevation view of a helical parafiin scraper surrounding a sucker rod which reciprocates within a string of pump tubing, the tubing being shown cut away so as to render the scraper visible and the figure being longitudinally broken for the purpose of illustrating that a greater number of convolutions of the helix than the number shown is contemplated as being within the scope of the invention.

Fig. 2 is a section view along the line 22 of Fig. 1.

Fig. 3 is an enlarged cross section taken transversely to the lead of the helix along line 33 of Fig. 1 to show the cross sectional shape thereof.

Fig. 4 is a cross sectional view similar to Fig. 3 but showing a modified form of cross section which may be used in the ambulatory scraper.

Fig. 5 is another view similar to Fig. 3 but showing still another modified form of cross section which may be used in the scraper.

Referring to the drawing, Fig. 1 illustrates a length of sucker rod R passing through a length of tubing T in which it reciprocates. Around the rod R and within the tubing T is disposed a helical paraffin scraper 1 according to the present invention and having a plurality of open convolutions, the total number of which may be varied for the purpose of providing adequate scraping coverage in a particular well. The scraper 1 as illustrated in Figs. 1, 2 and 3 is of rectangular cross section and includes radially disposed side surfaces 1a and longitudinal bearing surfaces 1b and 1c. The inner bearing surface 1b is intended to contact the sucker rod R, and the outer bearing surface 1c is intended to contact the inner surface of the tubing T. It will be noted that clearances are provided between the sucker rod and the inner bearing surface of the scraper and between the outer bearing surface of the scraper and the inner surface of the tubing T so that the scraper 1 will be free to reciprocate with respect to the tubing and the rod and also to migrate along the axial lengths of both in either direction until an abutment is struck.

Fig. 4 shows a modification of the cross section of the scraper 1, this modification being in the form of a truncated pyramid having sides 1d and having an inner surface 1e and an outer bearing surface 1 Another modification is illustrated in Fig. 5 having concave sides 1x and having an inner bearing surface ly and an outer bearing surface lz. It will be noted that each of these modifications has both inner and outer bearing surfaces 4 and that each of the modifications has substantially the same radial distance between the inner and the outer bearing surfaces, these surfaces being abruptly joined with the respective side surfaces to provide relatively sharp helical scraping edges.

Whatever cross sectional form is used in the scraper, the ends thereof are preferably cut off in the direction of a plane lying normal to the axis of the helix so as to provide fiat lands 2 at each end of the scraper on which surfaces the scraper will contact abutments (not shown) which limit the range of the scrapers travel on the sucker rod. In order to prevent snagging, the ends of the scraper, Fig. 2, should be somewhat rounded as at 3. The illustration in Fig. 1 is broken as at A to illustrate the fact that the number of convolutions of the scraper is not" limited to the number shown in the drawing. As stated above, any number of convolutions may be employed although it is not recommended that less than 1% or 2 convolutions be used so as to insure that the scraper will not cock on the sucker rod or within the tubing T.

A number of these scrapers have undergone very satisfactory tests under actual working conditions, these particular scrapers being formed of nylon which is one of the plastics having the properties set forth above.

The present invention is not to be limited to the exact form shown in the drawings, for other modifications are contemplated within the scope of the following claims.

I claim:

1. An ambulatory paraffin scraper in combination with a sucker rod having a length of substantially uniform diameter, and a tubing string having an inside diameter, the scraper consisting of at least one and one-half con volutions of plastic material describing an open helix having inner and outer bearing surfaces which respectively lie on the surfaces of two cylinders each coaxial with the helix, the diameter of the cylinder occupied by the inner bearing surface being larger than the diameter of the sucker rod, and the diameter of the cylinder occupied by the outer bearing surface being smaller than the inside diameter of the tubing string.

2. A scraper as set forth in claim 1 wherein the convolutions of plastic material consist of nylon.

References Cited in the file of this patent UNITED STATES PATENTS 1,639,660 Neumeyer Aug. 23, 1927 1,758,995 Armstrong et al May 20, 1930 1,891,615 Bostic Dec. 20, 1932 2,157,820 Fleck May 9, 1939 2,358,707 Haas Sept. 19, 1944 2,363,826 Yellin Nov. 28, 1944 2,453,199 Crall Nov. 9, 1948 2,595,025 Tripplehorn Apr. 29, 1952 2,679,905 Mangum et a1 June 1, 1954 2,695,673 Coyle Nov. 30, 1954 2,733,768 Tripplehorn Feb. 7, 1956 

